Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

Abstract

Fe-N-C materials are promising non-precious metal catalysts for the oxygen reductionreaction in fuel cells and batteries. However, during the synthesis of these materials less activeFe-containing nanoparticles are formed in many cases which lead to a decrease in electrochemicalactivity and stability. In this study, we reveal the significant properties of the carbon support requiredfor the successful incorporation of Fe-N-related active sites. The impact of two carbon blacks andtwo activated biomass-based carbons on the Fe-N-C synthesis is investigated and crucial supportproperties are identified. Carbon supports having low portions of amorphous carbon, moderatesurface areas (>800 m2/g) and mesopores result in the successful incorporation of Fe and N onan atomic level and improved oxygen reduction reaction (ORR) activity. A low surface area andespecially amorphous parts of the carbon promote the formation of metallic iron species coveredby a graphitic layer. In contrast, highly microporous systems with amorphous carbon provoke theformation of less active iron carbides and carbon nanotubes. Overall, a phosphoric acid activatedbiomass is revealed as novel and sustainable carbon support for the formation of Fe-Nxsites. Overall,this study provides valuable and significant information for the future development of novel andsustainable carbon supports for Fe-N-C catalysts.